The present invention relates to turbocharger systems for internal combustion engines, and, more particularly, to an interstage cooler for a turbocharger system.
A limiting factor in the performance of an internal combustion engine is the amount of combustion air that can be delivered to the intake manifold for combustion in the engine cylinders. Atmospheric pressure is often inadequate to supply the required amount of air for proper operation of an engine. Therefore, it is common practice to use an auxiliary system to supply additional air to the intake manifold. It is known to supply additional air to the intake manifold through the use of a turbocharger.
Turbochargers can be used to supply combustion air to an engine at a higher pressure and higher density than atmospheric pressure and ambient density. The turbocharger can be used to make up for loss of power due to altitude or to increase power that can be obtained from the engine of a given displacement, thereby reducing the cost, weight and size of an engine for a given power output.
A conventional multi-stage turbocharger includes a turbine section and two compressor sections. A common shaft interconnects the turbine wheel of the turbine section with compressor wheels in the compressor sections. A stream of exhaust gases from the engine is conducted from the exhaust manifold to the turbine section of the turbocharger. The stream of exhaust gases passing through the turbine section causes the turbine wheel to rotate, turning the shaft, and thereby rotating the compressor wheels in the compressor section. Ambient air to be used for combustion in the internal combustion engine is brought into an inlet for the first compressor section. The air is compressed by the first compressor wheel, and passes from the first compressor section through a first compressor section outlet to the inlet of the second compressor section, for further compression. The out flow from the second compressor section exits the turbocharger at the second compressor section outlet, and is directed to the inlet manifold of the internal combustion engine.
An interstage duct is used to conduct the compressed air from the first compressor section outlet to the inlet of the second compressor section. Foils or vanes near the compressor section inlets or outlets, or in the interstage duct, influence the compressed air stream flow. For example, diffuser vanes at the compressor section outlets are used to decrease air stream velocity and increase static pressure. Deswirling vanes near the second and subsequent inlets orient the air stream approaching the compressor wheel. Turning vanes may be used in the interstage duct to direct air flow around tight bends in the duct, to reduce losses in the duct.
One of the problems associated with the use of turbochargers is the build up of heat in the compressed air. Heat reduction has been accomplished through the use of external cooling units between the last compressor outlet and the intake manifold, so-called xe2x80x9caftercoolersxe2x80x9d. However, the build up of heat in the first compressor stage decreases the efficiency of the second compressor stage. To address this problem, so called xe2x80x9cinterstage coolersxe2x80x9d have been used to cool the airstream between compressor stages. Commonly, interstage coolers between the compression stages of a turbocharger have been designed with the use of an external heat exchanger through which the air is passed as it flows from a first compressor stage to a second compressor stage.
External interstage coolers provide no cooling of the turbocharger components themselves and can be bulky, utilizing additional space in what can be cramped environments around the internal combustion engine for which the turbocharger is used.
It is known from U.S. Pat. No. 4,193,738 to cool the adjustable nozzle vanes of a gas turbine engine by circulating a coolant fluid through the interior of the vane. A floating seal is provided to minimize leakage between the coolant flow circuit and the hot gas flow path.
The present invention is directed to overcoming one or more of the problems set forth above.
In one aspect of the invention, a multi-compressor turbocharger is provided with a rotatable shaft, and a multistage compressor including a first compressor wheel carried by the shaft, a first inlet associated with the first compressor wheel, a radially extending first outlet associated with the first compressor wheel, a second compressor wheel carried by the shaft, a second inlet associated with the second compressor wheel, and a radially extending second outlet associated with the second compressor wheel; an interstage duct fluidly interconnecting in series the first outlet of the first compressor wheel and the second inlet of the second compressor wheel; at least one heat exchanger disposed in the interstage duct; and a cooling fluid supply system fluidly connected to the heat exchanger.
In another aspect of the invention, a method of operation of a turbocharger includes: providing a multi-stage compressor including a first compressor wheel carried by the shaft, a first inlet associated with the first compressor wheel, a radially extending first outlet associated with the first compressor wheel, a second compressor wheel carried by the shaft, a second inlet associated with the second compressor wheel, and a radially extending second outlet associated with the second compressor wheel; an interstage duct fluidly interconnecting in series the first outlet of the first compressor wheel and the second inlet of the second compressor wheel; fluidly interconnecting in series the first outlet of the first compressor with the second inlet of the second compressor wheel using an interstage duct; positioning a heat exchanger within the interstage duct; rotating the first compressor wheel and the second compressor wheel carried by the shaft; and circulating a cooling fluid through the heat exchanger.